Ferruginous hawk numbers down in E. Washington

Ferruginous hawks, the largest soaring hawk, appear to be continuing to decline in Eastern Washington.

Washington Department of Fish and Wildlife biologists who conducted surveys this spring of known nesting territories counted fewer occupied nests than in 2002-03, the last year an extensive survey was conducted.

Because of budget constraints, biologists this year were unable to repeat the firsthand inspection and aerial surveys of nesting sites that they conducted in 2002-03. Instead, they relied on personal observation of known nesting sites of ferruginous hawks, which are listed as a threatened species in Washington and a federal species of concern.

There were 20 occupied nests in Benton and Franklin counties this year, some of which contained single adults, said Mike Livingston, district wildlife biologist for the Department of Fish and Wildlife.

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He did not have a breakdown of the number tallied in the two counties during the last survey. But in 2002-03, about 60 occupied nests were counted out of 115 known sites in all of Eastern Washington, he said.

“We didn’t have the money to do the aerial (surveys) this time so it isn’t completely comparable. But we do believe we are seeing a decline because this is their core range and we’re seeing a reduction in their core occupancy rates here,” Livingston said.

Department of Fish and Wildlife biologists in other parts of Eastern Washington also noted a drop in numbers of ferruginous hawks, which have a wingspan that can reach up to 4 feet.

Jeff Bernatowicz, biologist for Yakima and Klickitat counties, said only one of 13 known nesting sites he inspected was occupied. Landowners did not give his office access to several areas that were surveyed by air in 2003, he said.

On the Hanford Reach National Monument, no ferruginous hawks were counted at the 10 known nesting sites, said Heidi Newsome, biologist with the U.S. Fish and Wildlife Service’s Mid-Columbia National Wildlife Refuge complex.

Newsome said she did see one ferruginous hawk on the monument after doing the survey. “We’ll plan to check again in June,” she said.

Pat Fowler, southeast regional biologist, said he examined 21 of 30 known nesting sites, and only three or four contained hawks. There were up to eight active nests in the southeast corner of the state during the last survey, he said.

Loss of shrub-steppe habitat to development and a resulting drop in prey species for ferruginous hawks — including ground squirrels and black-tailed jackrabbits — have contributed to their decline in Eastern Washington, according to a Department of Fish and Wildlife study conducted more than seven years ago.

Ferruginous hawks are sensitive to disturbance from humans and have been known to abandon nests if human activity becomes too much for them, Livingston said.

The survey found about 25 percent of the 200 known ferruginous nesting territories were occupied in most years in Eastern Washington, and many of those sites had been vacant for years.

“The ecology of this hawk, more than any other Buteo (soaring hawk), is dependent on the native prairie ecosystems that are becoming increasingly rare and fragmented largely due to conversion to agriculture,” the study said.

In Eastern Washington, ferruginous hawks build their nests on rock faces, in isolated trees, in the middle of a small grove of trees or on electrical transmission towers. Their territory ranges from Canada into 17 states, and they migrate.

Ferruginous hawks that nest in Eastern Washington typically fledge their young in June. Then some migrate east of the Rocky Mountains to follow prey, according to a 2003 migration and winter range study of the hawks by the Department of Fish and Wildlife.

That study also found that some wintered in California.

One anecdotal sign of their relative scarcity in Eastern Washington comes from Blue Mountain Wildlife, a Pendleton-based nonprofit raptor rescue and rehabilitation group.

“We hardly ever get a ferruginous hawk,” said Lynn Tompkins, co-director. “We’ve had only a handful in 20 years.”